Floor for the equipment house - OSB boards or floorboards?

I will soon build my wooden equipment shed, which will stand on a profile wood frame on screw foundations. Now I am considering how to build the floor. The manufacturer standardly offers untreated 19mm boards for this, but these are currently not available, so that is out of the question. As an alternative, I have now researched OSB boards, but I am unsure about moisture because the house has a cavity underneath and accordingly, despite possible impregnation, mold could still form here. However, I could also be comfortable with simple KDI decking boards as an underfloor, which already provide appropriate protection from the start, are made of the same wood as the frame, and I could accordingly attach cross beams to the profile wood frame. Does anyone have experience with this? Or is there another alternative?

There are special OSB boards of class 3 or 4, which are (conditionally) suitable for outdoor use. Otherwise, there are also waterproof glued plywood boards, which are, for example, also used in trailers. Bauhaus has quite affordable offers. Cut edges must be sealed without fail.

I would use pressure-impregnated tongue and groove boarding.
Cheap, easy to work with, gives a decent, smooth floor.